Porous building and construction materials are widely used in various fields of building, building materials and so forth. As such porous building and construction materials, there may be mentioned, for example, architectural concrete, light-weight concrete, precast concrete, autoclaved light-weight concrete (ALC), asbestos slates, mortar, calcium silicate boards, pulp cement boards, cemented excelsior, gypsum boards, hard boards, plaster, bricks, blocks, tiles, gypsum plaster, dolomite plaster, natural stones, artificial stones, glass wool and other inorganic porous building and construction materials; and wood, plywood, particle boards and other organic porous building and construction materials.
Without thorough waterproofing treatment, moisture may penetrate into the interior of these porous building and construction materials and cause cracking due to expansion or the like and, in cases where there are reinforcing bars within said materials, may induce rusting of said reinforcing bars, which, in turn, may cause cracking due to expansion. Furthermore, if the waterproofing treatment is insufficient, the so-called color of wetting appears on the surface, causing a decrease in decorative effect.
So far, organosilicon compounds have been used as waterproofing agents for coating the surface of porous building and construction materials therewith or causing them to be absorbed by said materials to thereby prevent said materials from water absorption. They have a drawback, however, in that when used under conditions under which moisture remains on the material surface for a long period of time, they can no longer produce a sufficient waterproofing effect.
In Japanese Kokai Publication Hei-03-232527, there is disclosed a technology of using alkylalkoxysilanes as permeative, water absorption inhibitors for concrete by making them aqueous without using any solvent. This technology consists in making alkylakoxysilanes known to have a waterproofing effect aqueous by using a specific emulsifier to thereby prevent environmental pollution by organic solvents and, at the same time, attain a good waterproofing effect by causing said silanes to acquire a permeating ability. However, the effect is poor from the long-term effect viewpoint.
The decorative effect on porous building and construction materials has also been studied. In Japanese Kokai Publication Hei-05-124880, there is disclosed a method of finishing which comprises applying, to such materials, an undercoat composition comprising an aqueous silicone compound as a main component and then an overcoat composition comprising a fluororesin paint containing or free of a pigment. According to this technology, in addition to the above-mentioned waterproofing effect, a decorative effect can also be produced, giving an architectural concrete-like appearance, for instance.
However, this technology requires substrates to be coated twice, hence is troublesome to apply in field operation, and, at the same time, still has problems of reproducibility and quality maintenance.
In Japanese Kokai Publication Hei-04-33942, it is disclosed that an aqueous coating composition comprising an aqueous fluoroolefin-based resin dispersion (A) and an aqueous fluoroalkyl-containing resin dispersion (B) is useful as a coating composition having excellent weather resistance, chemical resistance, staining resistance and like properties. In this technology, however, the aqueous fluoroolefin-based resin dispersion (A) means an emulsion copolymer of various .alpha.,.beta.-ethylenically unsaturated compounds among which a fluoroolefin or fluoroolefins are main components (the above-cited publication, page 3, upper right column, lines 10 ff.) and the aqueous fluoroalkyl-containing resin dispersion (B) refers to an emulsion copolymer of various vinyl monomers among which a fluoroalkyl-containing vinyl monomer or monomers are main components (the above-cited publication, page 4, lower left column, lines 1 ff.), and both the constituents are thus restricted in their constitutions. The effects producible by said coating composition fail to include the expression of a waterproofing effect.
In Japanese Kokai Publication Hei-08-259892, it is disclosed that a resin composition for an aqueous coating composition which comprises a synthetic resin emulsion and an emulsion of a silicon compound and/or a partial hydrolyzate-condensate can form paint films excellent in weather resistance and water resistance. However, the synthetic resin emulsion to be used in this technology is a vinyl polymer or the like and the effects obtainable are restricted to weather resistance, staining resistance and the like.